1. Field of the Invention
The present invention relates to a rotary press having an additional printing apparatus and to a printing unit having an additional printing apparatus, wherein paper web is run while an image is being printed thereon by a rotating printing cylinder and wherein an additional image such as a spot image is printed thereon in alignment with the image printed by the printing cylinder.
2. Description of the Related Art
A conventional rotary press capable of performing additional printing is described, for example, in "Printing Engineering Handbook," Gihodo Shuppan, Jul. 20, 1987, 1st ed. (3rd impression), p. 887 (FIG. 5.11), p.889 (FIG. 5.13).
A printing unit which can perform additional printing and which constitutes such a conventional rotary press is shown in the above-cited "Printing Engineering Handbook," p. 887 (FIG. 5.12), p.889 (FIG. 5.14), and is disclosed in Japanese Patent Application Laid-Open (kokai) Nos. 62-173257 and 62-288039. Such a printing unit is adapted to print an image in black, for example, on both sides of paper web as well as an additional image in another color on either side of the paper web.
Also, a rotary press capable of performing additional printing is described in "Newspaper Technology 1996-4 No. 158," The Japan Newspaper Publishers and Editors Association, p. 131, right column, lines 8-10, reading "For the first time in the newspaper publishing industry, there is introduced a tower rotary press equipped with a spot-printing device at the top stack to thereby enable 4Hi spot-printing." This rotary press is denoted by "6T" in "Rotary Press Appearance" on page 133 of the publication. This rotary press is adapted to print printing images on both sides of paper web in black and three primary colors, as well as to print an additional image on either side in a special ink, such as a so-called special-color ink and a fluorescent ink which provide a brighter effect for a printed image than the above-mentioned black and three-primary-colors inks and an odorized ink.
In the above-cited "Rotary Press Appearance," printing units denoted by "P2," "P3," and "P4" correspond to the printing unit shown in FIG. 5.14 on page 889 of the aforementioned "Printing Engineering Handbook." "Rotary Press Appearance" shows a rotary press having an additional printing function.
An additional printing apparatus provided in a rotary press as well as in a printing unit is shown in the above-cited "Printing Engineering Handbook" at the upper left portion of FIG. 5.12 on page 887 and at the upper right portion of FIG. 5.14 on page 889.
Further, a conventional ink jet printing device is disclosed, for example, in International Patent Application Laid-Open (Kohyo) No. 63-500714.
As in other printing apparatuses, in the above-described conventional rotary presses having an additional printing apparatus, printing units having an additional printing apparatus, and additional printing apparatuses to be attached to such rotary presses or printing units, a printing plate is attached onto a printing cylinder, and ink is fed alone or together with dampening solution to the attached printing plate to thereby print an image on paper web through transfer of the image directly from the printing plate surface or via the surface of a blanket cylinder.
Accordingly, this kind of printing involves the following problems.
(1) An inking mechanism must be provided in order to feed ink to a printing cylinder and a printing plate attached to the printing cylinder for additional printing. In the case of offset printing, a dampening system must also be provided. Further, in order to align an additional image and an image to which the additional image is added, a registering device must be provided. Thus, an entire printing system requires a relatively large space for installation thereof and involves a number of diversified components, resulting in a large-scaled structure, increased cost of manufacture, and frequent maintenance.
(2) Since printing cylinders and inking mechanisms are provided in one-to-one correspondence, when a printing cylinder is axially divided into a plurality of regions having a predetermined width (e.g. 4 regions), it is quite difficult to print an additional image in a different ink at each of a plurality of locations in the same region or adjacent regions.
(3) A printing plate for additional printing must be prepared, thereby requiring process work and material for a printing plate as well as attachment/detachment of the printing plate.
(4) Maximum printing quantity depends on printing durability of a printing plate.